Involvement of dorsal raphe nucleus and dorsal periaqueductal gray 5-HT receptors in the modulation of mouse defensive behaviors

Previous findings point to the involvement of the dorsal raphe nucleus (DRN) and dorsal periaqueductal gray (dPAG) serotonergic receptors in the mediation of defensive responses that are associated with specific subtypes of anxiety disorders. These studies have mostly been conducted with rats tested in the elevated T-maze, an experimental model of anxiety that was developed to allow the measurement, in the same animal, of two behaviors mentioned: inhibitory avoidance and one-way escape. Such behavioral responses have been respectively related to generalized anxiety disorder (GAD) and panic disorder (PD). In order to assess the generality of these findings, in the current study we investigated the effects of the injection of 5-HT-related drugs into the DRN and dPAG of another rodent species, mouse, on the mouse defense test battery (MDTB), a test of a range of defensive behaviors to an unconditioned threat, a predator. Male CD-1 mice were tested in the MDTB after intra-DRN administration of the 5-HT(1A) receptor antagonist WAY-100635 or after intra-dPAG injection of two serotonergic agonists, the 5-HT1A receptor agonist 8-OH-DPAT and the 5-HT(2A/2C) receptor agonist DOI. Intra-DRN injection of WAY-100635 did not change behavioral responses of mice confronted with a rat in the MDTB. In the dPAG, both 8-OH-DPAT and DOI consistently impaired mouse escape behavior assessed in the MDTB. Intra-dPAG infusion of 8-OH-DPAT also decreased measures of mouse risk assessment in the rat exposure test. In conclusion, the current findings are in partial agreement with previous results obtained with rats tested in the elevated T-maze. Although there is a high level of similarity between the behavioral effects obtained in rats (elevated T-maze) and mice (MDTB and RET) with the infusion of 5-HT agonists into the dPAG, the same is not true regarding the effects of blockade of DRN 5-HT(1A) receptors in these rodent species. These data suggest that there may be differences between mice and rats regarding the involvement of the DRN in the mediation of defensive behaviors. (C) 2010 Elsevier B.V. and ECNP. All rights reserved.

Hematopoietic SCT modulates gut inflammation in experimental inflammatory bowel disease

Hematopoietic SCT (HSCT) and high-dose chemotherapy are being explored as therapy for various human refractory immune-mediated conditions, including inflammatory bowel diseases (IBD). Nevertheless, the exact immunological mechanisms by which the BM cells (BMCs) or immunosuppression provide remission from these diseases is not yet clear. In this work, we investigated the role of these therapies in the modulation of gut mucosal inflammation in an experimental model of IBD. Colitis was induced in mice by 2,4,6-trinitrobenzenesulfonic acid and after CY was administered (200 mg/kg) alone (CY group) or followed by BMCs infusion (HSCT group). Animals were followed for 60 days. Both HSCT and CY reduced the histopathological features of colitis significantly. Infused cells were localized in the gut, and a marked decrease of CD4(+) leukocytes in the inflammatory infiltrate on days +7 and +14 and of CD8(+) cells on day +7 was found in both treatments allied to impressive reduction of proinflammatory Th1 and Th17 cytokines. Although chemotherapy alone was the best treatment regarding the induction of immunosuppressive molecules, only HSCT resulted in increased survival rates compared with the control group. Our findings indicate that high-dose CY followed by HSCT is effective in the modulation of mucosal immunity and in accelerating immune reconstitution after BMT, thus providing valuable tools to support the development and understanding of novel therapeutic strategies for IBD. Bone Marrow Transplantation (2010) 45, 1562-1571; doi:10.1038/bmt.2010.6; published online 15 March 2010

Effect of acute restraint stress on the tachycardiac and bradycardiac responses of the baroreflex in rats

In the present study, we evaluated cardiac baroreflex responses of rats submitted to acute restraint stress. The baroreflex was tested: immediately before, during a 30 min exposure to restraint stress, as well as 30 and 60 min after ending the stress session (recovery period). Restraint increased both mean arterial pressure (MAP) and heart rate (HR). The magnitude of tachycardiac responses evoked by intravenous infusion of sodium nitroprusside was higher during restraint stress, whereas that of bradycardiac responses evoked by intravenous infusion of phenylephrine was decreased. Restraint-evoked baroreflex changes were still observed at 30 min into the recovery period, although MAP and HR values had already returned to control values. The baroreflex was back to control values at 60 min of the recovery period. Intravenous administration of the selective beta(1)-adrenoceptor antagonist atenolol blocked the restraint-evoked increase in the tachycardiac baroreflex response, but did not affect the effects on the bradycardiac response. In conclusion, the present results suggest that psychological stresses, such as those resulting from acute restraint, affect the baroreflex. Restraint facilitated the tachycardiac baroreflex response and reduced the bradycardiac response. Restraint-related effects on baroreflex persisted for at least 30 min after ending restraint, although MAP and HR had already returned to control levels. The cardiac baroreflex returned to control values 60 min after the end of restraint, indicating non-persistent effects of acute restraint on the baroreflex. Results also indicate that the influence of restraint stress on the baroreflex tachycardiac response is mainly dependent on cardiac sympathetic activity, whereas the action on the bradycardiac response is mediated by the cardiac parasympathetic component.

Non-N-methyl-d-aspartate glutamate receptors in the lateral hypothalamus modulate cardiac baroreflex responses in conscious rats

P>In the present study, we investigated the effects of inhibition of the lateral hypothalamus (LH) neurotransmission with bilateral microinjection of CoCl(2), a non-selective blocker of neurotransmission, on modulation of cardiac baroreflex responses in conscious rats as well as the involvement of LH glutamatergic neurotransmission in this modulation. Reflex bradycardiac and tachycardiac responses to blood pressure increases (following i.v. infusion of phenylephrine) or decreases (following i.v. infusion of sodium nitroprusside) were investigated in conscious male Wistar rats. Responses were evaluated before and after microinjection of 1 nmol/100 nL CoCl(2), 2 nmol/100 nL 1,2,3,4-tetrahydro-6-nitro-2,3-dioxobenzoquinoxaline-7-sulphonamide (NBQX; a selective non-N-methyl-d-aspartate (NMDA) glutamate receptor antagonist) or different doses (2, 4 or 8 nmol/100 nL) of the selective NMDA glutamate receptor antagonist LY235959. Microinjection of CoCl(2) into the LH had no effect on the tachycardiac baroreflex response, but did evoke a decrease in the reflex bradycardia caused by increases in blood pressure. Microinjection of NBQX into the LH had a similar effect on reflex bradycardia as CoCl(2), but had no effect on the tachycardiac response. Microinjection of increasing doses of LY235959 into the LH had no effect on the cardiac baroreflex response. In conclusion, the data suggest that the LH has a tonic facilitatory influence on the parasympathetic component of the baroreflex. The results also indicate that this facilitatory influence is mediated by local LH glutamatergic neurotransmission through non-NMDA glutamatergic receptors.

Insular cortex alpha(1)-adrenoceptors modulate the parasympathetic component of the baroreflex in unanesthetized rats

The insular cortex (IC) has been reported to modulate the cardiac parasympathetic activity of the baroreflex in unanesthetized rats. However, which neurotransmitters are involved in this modulation is still unclear. In the present study, we evaluated the possible involvement of local IC-noradrenergic neurotransmission in modulating reflex bradycardiac responses. Bilateral microinjection of the selective alpha(1)-adrenoceptor antagonist WB4101 (15 nmol/100 nL), into the IC of male Wistar rats, increased the gain of reflex bradycardia in response to mean arterial pressure (MAP) increases evoked by intravenous infusion of phenylephrine. However, bilateral microinjection of equimolar doses of either the selective alpha(2)-adrenoceptor antagonist RX821002 or the non-selective beta-adrenoceptor antagonist propranolol into the IC did not affect the baroreflex response. No effects were observed in basal MAP or heart rate values after bilateral microinjection of noradrenergic antagonists into the IC, thus suggesting no tonic influence of IC-noradrenergic neurotransmission on resting cardiovascular parameters. In conclusion, these data provide evidence that local IC-noradrenergic neurotransmission has an inhibitory influence on baroreflex responses to blood pressure increase evoked by phenylephrine infusion through activation of alpha(1)-adrenoceptors. (C) 2009 Elsevier B.V. All rights reserved.

Glutamate and the neural basis of the subjective effects of ketamine

Context: Ketamine evokes psychosislike symptoms, and its primary action is to impair N-methyl-D-aspartate glutamate receptor neurotransmission, but it also induces secondary increases in glutamate release. Objectives: To identify the sites of action of ketamine in inducing symptoms and to determine the role of increased glutamate release using the glutamate release inhibitor lamotrigine. Design: Two experiments with different participants were performed using a double-blind, placebo-controlled, randomized, crossover, counterbalanced-order design. In the first experiment, the effect of intravenous ketamine hydrochloride on regional blood oxygenation level dependent (BOLD) signal and correlated symptoms was compared with intravenous saline placebo. In the second experiment, pretreatment with lamotrigine was compared with placebo to identify which effects of ketamine are mediated by increased glutamate release. Setting: Wellcome Trust Clinical Research Facility, Manchester, England. Participants: Thirty-three healthy, right-handed men were recruited by advertisements. Interventions: In experiment 1, participants were given intravenous ketamine (1-minute bolus of 0.26 mg/ kg, followed by a maintenance infusion of 0.25 mg/ kg/ h for the remainder of the session) or placebo (0.9% saline solution). In experiment 2, participants were pretreated with 300 mg of lamotrigine or placebo and then were given the same doses of ketamine as in experiment 1. Main Outcome Measures: Regional BOLD signal changes during ketamine or placebo infusion and Brief Psychiatric Rating Scale and Clinician- Administered Dissociative States Scale scores. Results: Ketamine induced a rapid, focal, and unexpected decrease in ventromedial frontal cortex, including orbitofrontal cortex and subgenual cingulate, which strongly predicted its dissociative effects and increased activity in mid- posterior cingulate, thalamus, and temporal cortical regions (r= 0.90). Activations correlated with Brief Psychiatric Rating Scale psychosis scores. Lamotrigine pretreatment prevented many of the BOLD signal changes and the symptoms. Conclusions: These 2 changes may underpin 2 fundamental processes of psychosis: abnormal perceptual experiences and impaired cognitive- emotional evaluation of their significance. The results are compatible with the theory that the neural and subjective effects of ketamine involve increased glutamate release.

Occult risk factor for the development of cerebral edema in children with diabetic ketoacidosis: possible role for stomach emptying

The incidence of cerebral edema during therapy of diabetic ketoacidosis (DKA) in children remains unacceptably high-this suggests that current treatment may not be ideal and that important risk factors for the development of cerebral edema have not been recognized. We suggest that there are two major sources for an occult generation of osmole-free water in these patients: first, fluid with a low concentration of electrolytes that was retained in the lumen of the stomach when the patient arrived in hospital; second, infusion of glucose in water at a time when this solution can be converted into water with little glucose. In a retrospective chart review of 30 patients who were admitted with a diagnosis of DKA and a blood sugar > 900 mg/dL (50 mmol/L), there were clues to suggest that some of the retained fluid in the stomach was absorbed. To minimize the likelihood of creating a dangerous degree of cerebral edema in patients with DKA, it is important to define the likely composition of fluid retained in the stomach on admission, to look for signs of absorption of some of this fluid during therapy, and to be especially vigilant once fat-derived brain fuels have disappeared, because this is the time when glucose oxidation in the brain should increase markedly, generating osmole-free water.

Evaluation of hepatobiliary excretion and enterobiliary reflux in rats with biliary obstruction submitted to bilioduodenal or biliojejunal anastomosis

Bilioduodenal and biliojejunal anastomoses are effective for the treatment of biliary obstruction. The objective of this study was to compare the effects of these anastomoses on hepatobiliary excretion and enterobiliary reflux. Enterobiliary reflux and biliary excretion were evaluated respectively after oral administration of technetium (Tc-99m) in combination with sodium phytate and intravenous infusion of Tc-99m with diisopropyl-iminodiacetic acid. Enterobiliary reflux occurred to an equal degree in the bilioduodenal and biliojejunal groups. Maximum hepatic activity time (T-max) and radiotracer clearance half-time (T-1/2) were similar in both groups. However, when compared with that found for the sham-operated group, T-max, and T-1/2 were higher in the biliojejunal group (P = 0.02 and P = 0.01, respectively). Histopathological analysis showed marked reduction in ductal proliferation in both groups. These data undermine the theoretical advantages attributed to biliojejunal anastomosis and further the understanding of the pathophysiology of cholangitis that occurs even with patent anastomosis.

Short-Term Effects of Hydroxyethylstarch Resuscitation on Systemic and Regional Hemodynamics and Metabolism in a Brain-Dead Canine Model

Background. Hydroxyethylstarch (HES) is a synthetic polymer of glucose that has been suggested for therapeutic use in long-term plasma expansion. The aim of this study was to test the hypothesis that the infusion of a small volume of HES may provide benefits in systemic and regional hemodynamics and metabolism in a brain-dead canine model compared with large volume crystalloid resuscitation. Methods. Fourteen mongrel dogs were subjected to a brain-death protocol by consecutive insufflations of a balloon catheter in the epidural space. One hour after induction of brain-death, the animals were randomly assigned to two groups: NS (0.9% NaCl, 33mL/kg), and HES (6% HES 450/0.7, 17mL/Kg). Systemic and regional hemodynamics were evaluated using Swan-Ganz, ultrasonic flowprobes, and arterial catheters. Serial blood samples were collected for blood gas, electrolyte, and serum chemistry analysis. Systemic, hepatic, and splanchnic O(2)-derived variables were also calculated. Results. Epidural balloon insufflations induced a significant increase in mean arterial pressure, cardiac output (MAP and CO, respectively), regional blood flow, and systemic vascular resistance. Following the hyperdynamic phase, severe hypotension with normalization of systemic and regional blood flow was observed. Fluid resuscitation induced a prompt increase in MAP, CO, and portal vein blood flow, and a significant reduction in systemic and pulmonary vascular resistance. There were no differences between groups in metabolic indices, liver function tests (LFTs), or renal function tests. HES was more effective than NS in restoring cardiac performance in the first 2h after fluid resuscitation (P < 0.05). Both tested solutions partially and temporarily restored systemic and regional oxygen delivery. Conclusion. Small volumes of 6% HES 450/0.7 improved cardiovascular performance and provided the same regional hemodynamic and metabolic benefits of large volumes of isotonic crystalloid solutions. (C) 2011 Elsevier Inc. All rights reserved.

Effects of Nicotine Exposure on Renal Function of Normal and Hypercholesterolemic Rats

Background/Aims: Renal risks of nicotine exposure associated with hypercholesterolemia are still unknown. Methods: Thus, hypercholesterolemic rats (HC) and their control (C) were evaluated by inulin clearance (InCl) measured at baseline and during nicotine infusion (100 mu g/kg b.w.). Five groups were studied: (i) C; (ii) DEN (C submitted to a renal denervation); (iii) C + L-arginine (0.25% in drinking water); (iv) HC, and (v) HC + L-arginine (0.25% in drinking water). Furthermore, C and HC had their renal blood flow (RBF) measured and they have also been chronically treated with nicotine (12.5 mu g/ml in drinking water) to assess InCl on the 8th day. Results: Nicotine increased blood pressure in C, DEN and HC and reduced InCl only in C. L-Arginine treatment blunted nicotine effects on blood pressure and increased InCl only in C. Moreover, nicotine did not change RBF in C but elicited in HC, whereas renal vascular resistance was increased in C and unchanged in HC. Indeed, chronic nicotine exposure has also reduced InCl in C. Conclusion: Nicotine acted on the adrenergic system and nitric oxide counteracted this action in C, but the same may not be applied to HC. An impairment in renal autoregulation may explain why InCl was unchanged in HC. Copyright (C) 2009 S. Karger AG, Basel

Protective effects of carvedilol on systemic vascular damage induced by angiotensin II: Organ-specific effects independent of antihypertensive effects

Background: The protective effect of carvedilol on multiple organ damage induced by angiotensin II (Ang II) remains unclear. The aim of this study was to evaluate the protective effect of carvedilol on the heart, liver, and kidney in rats infused with Ang II. Material/Methods: Wistar rats were randomly distributed into three groups: control (no treatment), continuously infused with Ang II (150 eta g/min for 72 hr), and treated with Ang II + carvedilol (90 mg/kg/d). Histological sections of the myocardium, kidney, and liver were analyzed for the presence of necrosis. Results: Ang II induced arterial hypertension which was not affected by carvedilol treatment (tail-cuff blood pressures, control: 125 +/- 13.6, Ang II: 163 +/- 27.3, Ang II + CV: 178 +/- 39.8 mmHg, p<0.05). Also, there were perivascular inflammation and necrosis in the myocardium, kidney, and hepatocytes necrosis around the terminal vein. Carvedilol treatment fully prevented damage to the heart and kidney and attenuated liver lesions induced by the Ang II infusion. Conclusions: The protective effect of carvedilol on perivascular damage induced by Ang II infusion depended on the target organ. The prevention of heart damage occurred independently of the antihypertensive effects of carvedilol.

The GABAergic system contributes to the anxiolytic-like effect of essential oil from Cymbopogon citratus (lemongrass)

Ethnopharmacological relevance: The essential oil (EO) from Cymbopogon citratus (DC) Stapf is reported to have a wide range of biological activities and is widely used in traditional medicine as an infusion or decoction. However, despite this widely use, there are few controlled studies confirming its biological activity in central nervous system. Materials and methods: The anxiolytic-like activity of the EO was investigated in light/dark box (LDB) and marble-burying test (MBT) and the antidepressant activity was investigated in forced-swimming test (FST) in mice. Flumazenil, a competitive antagonist of benzodiazepine binding and the selective 5-HT(1A) receptor antagonist WAY100635 was used in experimental procedures to determine the action mechanism of EO. To exclude any false positive results in experimental procedures, mice were submitted to the rota-rod test. We also quantified some neurotransmitters at specific brain regions after EO oral acute treatment. Results: The present work found anxiolytic-like activity of the EO at the dose of 10 mg/kg in a LDB. Flumazenil, but not WAY100635, was able to reverse the effect of the EO in the LOB, indicating that the EO activity occurs via the GABA(A) receptor-benzodiazepine complex. Only at higher doses did the EO potentiate diethyl-ether-induced sleeping time in mice. In the FST and MBT, EO showed no effect. Finally, the increase in time spent in the light chamber, demonstrated by concomitant treatment with ineffective doses of diazepam (DZP) and the EO, revealed a synergistic effect of the two compounds. The lack of activity after long-term treatment in the LDB test might be related to tolerance induction, even in the DZP-treated group. Furthermore, there were no significant differences between groups after either acute or repeated treatments with the EO in the rota-rod test. Neurochemical evaluation showed no amendments in neurotransmitter levels evaluated in cortex, striatum, pons, and hypothalamus. Conclusions: The results corroborate the use of Cymbopogon citratus in folk medicine and suggest that the anxiolytic-like effect of its EO is mediated by the GABA(A) receptor-benzodiazepine complex. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Bacterial leakage evaluation of root canals filled with different endodontic sealers

Objective. The objective of this study was to evaluate the sealing ability of AH Plus, Epiphany, Acroseal, Endofill, and Polifil after active lateral condensation technique, by using a bacterial test, during 64 days. Study design. One hundred bovine incisors were cleaned and shaped; then they were filled with the endodontic sealers and adapted into a microcentrifuge tube. The setup root/microcentrifuge tube was added to glass flasks containing Brain Heart Infusion broth. A culture of Enterococcus faecalis was inserted into the upper chamber of each assembly. Daily leakage was evaluated through the broth turbidity. Results. The results were submitted to statistical analysis (Kaplan-Meier method, Kruskal-Wallis and Dunn tests). Conclusions. AH Plus and Endofill had the worst sealing ability when compared with Polifil, which showed the least leakage. Acroseal and Epiphany showed a tendency toward having an intermediate behavior; however, there was no significant difference among Acroseal, Epiphany, and the other sealers. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 108: e56-e60)

High doses of dexamethasone induce increased beta-cell proliferation in pancreatic rat islets

Rafacho A, Cestari TM, Taboga SR, Boschero AC, Bosqueiro JR. High doses of dexamethasone induce increased beta-cell proliferation in pancreatic rat islets. Am J Physiol Endocrinol Metab 296: E681-E689, 2009. First published January 21, 2009; doi:10.1152/ajpendo.90931.2008.-Activation of insulin signaling and cell cycle intermediates is required for adult beta-cell proliferation. Here, we report a model to study beta-cell proliferation in living rats by administering three different doses of dexamethasone (0.1, 0.5, and 1.0 mg/kg ip, DEX 0.1, DEX 0.5, and DEX 1.0, respectively) for 5 days. Insulin sensitivity, insulin secretion, and histomorphometric data were investigated. Western blotting was used to analyze the levels of proteins related to the control of beta-cell growth. DEX 1.0 rats, which present moderate hyperglycemia and marked hyperinsulinemia, exhibited a 5.1-fold increase in beta-cell proliferation and an increase (17%) in beta-cell size, with significant increase in beta-cell mass, compared with control rats. The hyperinsulinemic but euglycemic DEX 0.5 rats also showed a significant 3.6-fold increase in beta-cell proliferation. However, DEX 0.1 rats, which exhibited the lowest degree of insulin resistance, compensate for insulin demand by improving only islet function. Activation of the insulin receptor substrate 2/phosphatidylinositol 3-kinase/serine-threoninekinase/ribosomalprotein S6 kinase pathway, as well as protein retinoblastoma in islets from DEX 1.0 and DEX 0.5, but not in DEX 0.1, rats was also observed. Therefore, increasing doses of dexamethasone induce three different degrees of insulin requirement in living rats, serving as a model to investigate compensatory beta-cell alterations. Augmented beta-cell mass involves beta-cell hyperplasia and, to a lower extent, beta-cell hypertrophy. We suggest that alterations in circulating insulin and, to a lesser extent, glucose levels could be the major stimuli for beta-cell proliferation in the dexamethasone-induced insulin resistance.

Single Intranasal Administration of 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine in C57BL/6 Mice Models Early Preclinical Phase of Parkinson`s Disease

Many studies have shown that deficits in olfactory and cognitive functions precede the classical motor symptoms seen in Parkinson`s disease (PD) and that olfactory testing may contribute to the early diagnosis of this disorder. Although the primary cause of PD is still unknown, epidemiological studies have revealed that its incidence is increased in consequence of exposure to certain environmental toxins. In this study, most of the impairments presented by C57BL/6 mice infused with a single intranasal (i.n.) administration of the proneurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (1 mg/nostril) were similar to those observed during the early phase of PD, when a moderate loss of nigral dopamine neurons results in olfactory and memory deficits with no major motor impairments. Such infusion decreased the levels of the enzyme tyrosine hydroxylase in the olfactory bulb, striatum, and substantia nigra by means of apoptotic mechanisms, reducing dopamine concentration in different brain structures such as olfactory bulb, striatum, and prefrontal cortex, but not in the hippocampus. These findings reinforce the notion that the olfactory system represents a particularly sensitive route for the transport of neurotoxins into the central nervous system that may be related to the etiology of PD. These results also provide new insights in experimental models of PD, indicating that the i.n. administration of MPTP represents a valuable mouse model for the study of the early stages of PD and for testing new therapeutic strategies to restore sensorial and cognitive processes in PD.